The present invention relates to a video signal playback apparatus, and more particularly to a circuit for compensating for a drop-out of a reproduced video signal which is caused by damage or defects in the magnetism of the video tape in a video tape recorder (VTR) or video cassette recorder (VCR).
In general, when drop-out (loss of signal due to damage to a tape or its magnetism) occurs, an apparatus for compensating for the loss of reproduced FM signal signals in a video signal reproducing apparatus counteracts the drop-out by outputting a delayed video signal from a 1H delay circuit. In other words, a one horizontal scan line delayed (1H-delayed) signal is selected and outputted instead of the original signal in response to a detecting pulse produced when, the drop-out occurs. Since television signals have a close line correlation between one another, that is, signals before and after a 1H delay are almost identical, their drop-out can be completely compensated for. However, if the amplitude levels do not match when attempting to adjust the output level of the 1H delay circuit to that of the original signal, the compensation effect lessens, and sometimes the quality of picture suffers.
FIG. 1 shows a conventional drop-out compensator. Referring to FIG. 1, the resistance of variable resistor VR is adjusted to set the output level of a 1H delay circuit to that of the original signal. At this time, since the user sets the level while watching a screen, the levels are difficult to match precisely. Further, exact settings will vary according to the one who adjusts, the level and in particular will shift due to the variation of the resistance according to vibration and temperature, resulting in the above mentioned problems.